Available epidemiologic studies, from around the world, provide evidence for association between the incidence of lung and other cancers and exposure to aflatoxins in contaminated grain dust. In the United States, limited exposure data are currently available to assess the potential risk of lung cancer in farmers and agricultural workers due to inhalation of aflatoxin contaminated grain dust. Past analysis of grain dust samples from the midwest and southeast corn growing belt has demonstrated the presence of aflatoxins in high volume samples of airborne dust. Recent drought conditions have led to flourishing fungal growth and consequent production of alarming levels of aflatoxins in the corn crop. Our preliminary study indicates once detected aflatoxin B1 in airborne dust samples collected during harvesting, continues throughout grain unloading and animal feeding. The possibility for repeated hot and humid seasons creates a growing need to define the possible role of aflatoxins in the etiology of lung or other cancers. Current analytical methods are time consuming and lack the sensitivity, selectivity and versatility needed for accurate quantitative determination of the total dose resulting from small repeated exposures. The proposed work is intended to develop and validate laboratory and field methods for accurate determination of the average yearly exposure of farmers to aflatoxins, particularly, aflatoxin B1 in respirable dust from the harvesting process as well as other on-farm grain handling operations. The proposed analytical method is based on the use of supercritical fluid extraction (SFE) on-line with gas chromatography or supercritical fluid chromatography followed by mass spectrometric detection (SFE/GC/MS or SFE/SFC/MS). Our preliminary data with SFE demonstrates that this method is much faster, more sensitive, more selective and provide more reliable quantification than existing liquid extraction method. The new method will be used to collect an initial exposure data base for future epidemiologic assessments of the cancer risk associated with aflatoxin inhalation. This method should also ensure accurate assessment of the occupational exposure to other mycotoxins (e.g. zearalenone, vomitoxin, ochratoxin, and newly discovered fumonisin) which may be detectable during the course of aflatoxin analysis.